Channel balance

Hello,

With this combination of attachments, you could have either an S380-30 or S385-30 channel balance. You’ll need to measure as shown below. The Series 380 has a 1" bottom attachment, and the Series 385 has a 1-3/32" attachment. 

You'll also need to weigh your sash to determine which option you'll need. There is a chart on the product page that explains how to choose your option based on the sash weight.

Thank you and let us know if you have any other questions or concerns.

Comparison of the S378, S380 and S385 balance shoes.

Unfortunately, your 2990 balance stamp is from an outdated weight system that is no longer used. Weighing the sash and following the balance chart under the product description is the only way to ensure that you get the correct spring strength for your window.